FILE - In this March 23, 2010, file photo, installers from California Green Design install solar electrical panels on the roof of a home in Glendale, Calif. The Obama administration is boosting the development of solar and wind energy on public lands. A final rule announced by the Interior Department on Thursday, Nov. 10, 2016, would create a new leasing program on public lands and encourage development in areas where it would have fewer effects on the environment. (AP Photo/Reed Saxon, File)

The tech giant has signed deals with renewable energy producers. Google, like other companies, buys renewable energy up front, allowing the producers to expand and add their clean energy to normal power grids.

This photo provided by Google shows windmills at a wind farm in Minco, Okla., that provides Google with some of its renewable energy. Google says it believes that beginning in 2017, it will have amassed enough renewable energy to meet all of its electricity needs throughout the world. (Tim Boyles Photography/Google via AP)

Joe Kava, Google's senior vice president of technical infrastructure, said wind was better than fossil fuels since its prices are more static, so it can plan better. And buying more renewable energy makes it cheaper.

It's good for the economy, good for business and good for our shareholders.

Joe Kava

Google claims it's the world's largest buyer of clean energy, which is hard to verify. It bought 5.7 terawatt-hours of clean energy in 2015, which experts say is roughly two coal power plants' worth.

Google clearly needs every last drop, since the search engine giant used as much energy as the city of San Francisco last year.

What's Google's competition doing?

Other Silicon Valley leaders have made dramatic shifts to use more clean energy.

Amazon reiterated a long-term commitment to solar power last week, though it isn't quite at Google's usage of clean energy yet.

Here's how Google stacks up to the competition, according to the press release.

'PR gimmick'

But critics have raised doubts, since much of so-called "clean" energy is intermittent, while Google can't exactly afford to have YouTube or its search engine go down at any point. That means it still relies heavily on fossil fuels -- for now.